In the manufacture of various types of devices, such as semiconductor devices, an exposure apparatus which forms a latent pattern on a photosensitive agent applied to a substrate is used. The latent pattern is patterned in a later developing step. One of the important factors in the exposure apparatus can include an exposure processing ability, i.e., the throughput.
As a scheme that greatly improves the throughput, a scheme is available which simultaneously performs an alignment process (a measurement process for alignment) and an exposure process (a process of forming a latent pattern on a substrate while positioning the substrate on the basis of information obtained by the alignment process). According to this scheme, two stages are provided. The alignment process is performed for a substrate on the stage in an alignment process area, and the exposure process is performed for a substrate on the stage in an exposure process area. When the simultaneous processes are ended, the stage which holds the aligned substrate is moved from the alignment process area into the exposure process area, and the stage which holds the exposed substrate is moved from the exposure process area into the alignment process area.
According to this scheme, the two stages must be swapped between the alignment process area and the exposure process area. An exposure apparatus is available which moves two stages on one stage base in order to swap them. If the two stages are arranged on one stage base, when the alignment process and exposure process are to be performed simultaneously, vibration which can be caused by a reaction force generated upon driving one stage adversely affects driving and positioning of the other stage. More specifically, the reaction force which accompanies driving of one stage can decrease the positioning accuracy of the other stage, or prolong the settling time during positioning.
Japanese Patent Laid Open No. 2001-203140 discloses the following exposure apparatus. Two stage bases are arranged on a base plate. A stage main body which is movable in X and Y directions is arranged on each stage base. Wafer tables are held by the conveyance arm mechanisms of conveyance mechanisms, and are swapped between the two stage main bodies. In the exposure apparatus disclosed in this reference, vibration that can be generated by one stage main body is prevented from being transmitted to the other stage main body.
With the wafer table swapping scheme disclosed in this reference, in addition to wafer or wafer table positioning mechanisms, to swap the two wafer tables, the conveyance mechanisms that drive the two wafer tables two-dimensionally are indispensable. The conveyance mechanisms do not share components with the wafer or wafer table positioning mechanisms, but are completely independent, making the structure of the exposure apparatus complicated.
The conveyance mechanisms for swapping the wafer tables disclosed in Japanese Patent Laid Open No. 2001-203140 cannot swap the positions of the two conveyance arm mechanisms that respectively hold the wafer tables. Therefore, while the two conveyance arm mechanisms respectively hold the wafer tables, the two wafer tables cannot be simultaneously swapped between the two stage main bodies. Accordingly, the conveyance mechanisms for swapping the wafer tables disclosed in this reference require a long period of time for swapping the wafer tables.